1. Field of the Invention
The present invention relates to a vacuum circuit breaker, and particularly, to a vacuum circuit breaker capable of molding a vacuum interrupter by epoxy, and symmetrically arranging main circuit units at a center portion of a driving unit.
2. Background of the Invention
A switchgear serves to monitor or control or protect an electricity system used to transmit or to distribute power received from a power plant or a substation to a house. This switchgear consists of a structure for supporting or protecting unitary devices (circuit breaker, protection relay, etc.) attached thereto, and wires for connecting the unitary devices to each other. And, the switchgear is categorized into a gas insulation switchgear and an air insulation switchgear according to an insulation method therein. In the aspects of functions, the switchgear may be classified into a switchgear for monitoring an electricity system, a switchgear for opening and closing an electricity system, a switchgear for converting power by a semiconductor device, etc., and so on.
A circuit breaker is an electricity protecting apparatus capable of protecting a load device and a line from an accidental current due to a shortening, a ground accident, etc. that may occur on an electric circuit. According to an extinguishing medium, the circuit breaker is classified into an oil circuit breaker using oil as an extinguishing medium, a gas circuit breaker using sulfur hexafluoride (SF6), inactive gas, an air circuit breaker using air as an extinguishing medium, a vacuum circuit breaker using a vacuum state, etc. Hereinafter, the vacuum circuit breaker of the switchgear for opening and closing an electricity system will be explained.
FIG. 1 is a perspective view of a vacuum circuit breaker in accordance with the conventional art, and FIG. 2 is a perspective view of main circuit units of the vacuum circuit breaker of FIG. 1, which is shown from a different angle from FIG. 1.
As shown, the conventional vacuum circuit breaker comprises a driving unit 10 configured to generate a driving force, main circuit units 20 configured to break a circuit by using a driving force generated from the driving unit 10, and a frame unit 30 installed between the driving unit 10 and the main circuit units 20, and configured to transmit a driving force generated from the driving unit 10 to the main circuit units 20.
A rotation shaft 11 for transmitting a driving force is installed at the driving unit 10. And, a connection member 12 and a conversion link 13 for converting a rotary motion of the rotation shaft 11 to a horizontal motion of a transfer link 31 to be later explained are coupled to the rotation shaft 11. The connection member 12 is integrally coupled to the rotation shaft 11, and the conversion link 13 is rotatably coupled to the connection member 12.
The main circuit units 20 include an epoxy housing 21, a vacuum interrupter 22 mounted in the epoxy housing 21, an upper conductor 23 and a lower conductor 24 coupled to conductors disposed at both sides of the vacuum interrupter 22, and an insulation rod 25 coupled to the frame unit 30 and operating the vacuum interrupter 22 by a driving force transferred through the frame unit 30.
The epoxy housing 21 is formed in a hollow cylindrical shape, and the vacuum interrupter 22 is vertically installed at an inner space of the housing 21 with an interval from an inner circumferential surface of the epoxy housing 21. The upper conductor 23 and the lower conductor 24 are inserted into the epoxy housing 21 in a horizontal direction, thereby being mechanically coupled to conductors (not shown) of the vacuum interrupter 22. Under these configurations, the vacuum interrupter 22 is supported at the epoxy housing 21 by the upper conductor 23 and the lower conductor 24.
The frame unit 30 includes a transfer link 31, a supporting plate 32, a spring guide 33, a direction conversion link 34, a contact pressure spring 35, etc., and is configured to convert a rotary motion of the rotation shaft 11 into a horizontal motion.
The conventional vacuum circuit breaker rotates the rotation shaft 11 by using a driving force generated from the driving unit 10.
A rotary force of the rotation shaft 11 is converted into a linear force via the connection member 12 and the conversion link 13, and then is transferred to the transfer link 31 of the frame unit 30. The transfer link 31 is moved to a horizontal direction by the conversion link 13.
The horizontal motion in back and forth directions is converted into a vertical motion, through the contact pressure spring 35 and the direction conversion link 34 connected to the transfer link 31. As the insulation rod 25 and a movable contact inside the main circuit units 20 vertically move, the movable contact comes in contact with a fixed contact. Even after the movable contact has come in contact with the fixed contact, the rotation shaft 11 rotated by a driving force generated from the driving unit 10 continues to receive a rotary force. As a result, the transfer link 31 receives a force to continue a horizontal motion. However, the direction conversion link 34 is not moved any longer. Accordingly, the spring supporting plate 32 is horizontally moved along the spring guide 33 thereby to compress the contact pressure spring 35. In a state that the contacts have a constant contact pressure therebetween, a closing operation is completed. This may allow the contact pressure to overcome an electronic repulsive force during a current flowing operation, and to be utilized as energy during a current breaking operation.
On the contrary, when separating the movable contact from the fixed contact by removing a latch for maintaining a closed state from the driving unit 10, an opening operation is performed in a direction opposite to that of the closing operation.
The conventional vacuum circuit breaker may have the following problems.
Firstly, one main circuit unit 20 is implemented by assembling the epoxy housing 21, the vacuum interrupter 22, the upper conductor 23 and the lower conductor 24 to one another. This may increase fabrication time and may cause assembly errors.
Secondly, the frame unit 30 is eccentrically installed to the right side or the left side with respect to the driving unit 10. Accordingly, when the upper conductor 23 and the lower conductor 24 installed on side surfaces of the main circuit unit 20 are rotated by 180°, the upper conductor 23 and the lower conductor 24 cannot obtain a sufficient insulation distance from a panel of the switchgear. This may increase a width of the panel of the switchgear to increase a size of the switchgear.